The present invention relates to a pressure modulator for an anti-lock braking (ABS) system.
Anti-lock braking system controls the fluid pressure of the brake supplied to a wheel brake or cylinder to prevent the brake from locking up or skidding, therefore maximizing the stopping capabilities of a vehicle while allowing maximum maneuverability of the vehicle. Most anti-lock braking systems have a wheel speed sensor which provides an input to a controller. The controller outputs a signal when ABS operation is required. A pressure modulator of some type then takes over and in response to signal given by the controller applies, holds or decrease the pressure supplied to the wheel brake. One control algorithm is described in U.S. Pat. No. 4,673,225 issued on Jun. 16, 1987. Anti-lock braking system moudlators are shown and described in U.S. Pat. No. 4,653,815 issued on Mar. 31, 1987, U.S. Pat. No. 4,756,391 issued on Jul. 12, 1988, U.S. Pat. No. 5,000,523 issued on Mar. 19, 1991, U.S. Pat. No. 5,011,237 issued on Apr. 30, 1991, and U.S. Pat. 5,071,202 issued on Dec. 10, 1991.
An object of the present invention is to improve a cam actuated anti-lock braking system modulator such that a high efficiency simple drive including the cam moves a piston toward a predetermined extreme position.